1. Field of the Invention
The present invention relates to an internal combustion engine controller and, more specifically, to a control technique reducing the number of rotations of an output shaft of the internal combustion engine at the time of gear shifting.
2. Description of the Background Art
Conventionally, a vehicle having manual transmission has been known, in which gear shifting is done manually while the clutch is disengaged by a driver operation on a clutch pedal. In such a vehicle, a shock comes when the clutch is engaged again after gear shifting, if the number of rotations of an output shaft of the engine does not match the number of rotations of an input shaft of the transmission. Therefore, a technique of attaining synchronization between the number of rotations of an output shaft of the engine and the number of rotations of an input shaft of the transmission at the time of gear shifting has been proposed.
Japanese Patent Laying-Open No. 2001-74135 discloses a transmission control device capable of suppressing generation of the shock experienced at the time of shift change, that is, the shift shock. The transmission control device described in Japanese Patent Laying-Open No. 2001-74135 includes, in a manual transmission vehicle including an engine and a manual transmission connected to the engine through a clutch, a transmission input shaft rotation number detecting unit for detecting the number of rotations of the input shaft of the manual transmission, on the input shaft side of the manual transmission, and a control unit controlling engine speed (number of rotations) of the engine such that it is synchronized with the number of rotations of the input shaft of manual transmission in accordance with a detection signal from the transmission input shaft rotation number detecting unit, regardless of an accelerator position, when the clutch is disengaged (released). The control unit determines an amount of control reflecting the difference between the number of rotations of the input shaft of the manual transmission and the engine speed at the time of an up-shifting from a preset map, and controls the engine speed based on the amount of control, so that the engine speed decreases. Further, when the difference between the number of rotations of the input shaft of the manual transmission and the engine speed is not larger than a prescribed value, the control unit determines an amount of control found from the preset map to be zero, so that engine speed control is not performed.
According to the transmission control device in accordance with this laid-open application, the control unit has a function of controlling the engine speed such that it is synchronized with the number of rotations of the input shaft of manual transmission in accordance with a detection signal from the transmission input shaft rotation number detecting unit, regardless of an accelerator position when the clutch is disengaged, and therefore, the shock at the time of shift change, that is, the shift shock, can be suppressed. Further, the control unit additionally has a function of determining the amount of control reflecting the difference between the number of rotations of the input shaft of the manual transmission and the engine speed at the time of an up-shifting from a preset map and controlling the engine speed based on the amount of control, so that the engine speed decreases. Therefore, even when the driver shifts the gear up (up-shift) while continuously pressing the acceleration pedal, the difference between the engine speed and the number of rotations of the input shaft of the manual transmission can automatically be absorbed, and efficient transmission control is possible. Further, the control unit additionally has a function of determining the amount of control found from a preset map to be zero, so as not to perform engine speed control. Therefore, engine speed control is not performed when the difference between the number of rotations of the input shaft of the manual transmission and the engine speed is not larger than a prescribed value, that is, when the vehicle is started from the stopped state, and therefore, a factor that may hinder the half-clutch starting operation can be avoided.
In an engine having inertia mass of a flywheel or intake volume enlarged in order to increase engine output, even when the accelerator is set to the full close position for an up-shift, sometimes the engine speed still continues to increase for a while. Therefore, if engine speed control is not performed when the difference between the number of rotations of the input shaft of the manual transmission and the engine speed is not larger than a prescribed value, as in the transmission control device described in the laid-open application mentioned above, the difference in the number of rotations would be considerably large by the time the clutch is re-engaged, even if the difference is small at the start of gear shifting. If the clutch is re-engaged in this state, a shift shock is likely.